本論文使用分子動力學模擬單晶銅極低溫狀態下的剪切行為，並且探討析出物對塑性變形行為的影響。針對不同的剪切晶面與方向、作用速度、析出物大小及距離探討其塑變行為。銅塊材使用嵌入式(EAM)勢能函數建構其模型，利用剛性邊界的移動方式使材料晶體結構產生塑性變形。本論文所探討的內容可分為兩部分：(1)針對ModeⅡ及ModeⅢ進行材料機械性質的研究，(2)析出物對ModeⅡ及ModeⅢ剪切方式機制的影響。剪切過程中，針對刃差排、雙晶變形、差排堆積、交滑及差排環等材料微觀結構之缺陷作深入探討，並利用剪力關係加以分析。
模擬結果顯示，ModeⅡ剪切含析出物的晶體比無析出物者之剪切力高。其中，以(101)[101 ̅]的剪切行為的剪切力震盪最大，其次為(111)[1 ̅10]與(001)[100]的剪切，故(101)[101 ̅]剪切過程中受到析出物影響最大；而材料含多個析出物時，隨著析出物間距愈大，其對差排移動所構成的阻礙相對較小，因此在差排遭遇析出物的瞬間剪力值不會有明顯的提升；但當析出物間距愈小時，其差排所需的驅動力要愈大才能使越過障礙物。故析出物的分佈越緻密時，材料的塑變應力則越大。在ModeⅢ剪切時，FCC晶體結構會以{111}劈裂面產生脆性劈裂破壞之形貌呈現。

In this thesis, mechanical properties and shear behavior of the single-crystal copper were simulated at low extremely temperature by molecular dynamics(MD), and those effects of precipitates on plastic behavior were discussed. Besides, plastic deformation behavior for different shear planes, orientations, moving rates, precipitate size and distance were also discussed. The Cu blocks were described by the EAM potential function to build up the model；the plastic deformation of the lattice structure of the material were produced by the moving rigid boundary. This thesis is separated into two part：(i) mechanical properties of materials of modeⅡ and modeⅢ, and (ii) the shear effects of precipitates of modeⅡ and modeⅢ. During shear processes, microstructure defects such as edge dislocations, twinning deformation, dislocation piling up, cross slip and dislocation loop were discussed and analyzed with the relationship of shear force.
Results show that the shear stress for the crystal containing precipitates was higher than the crystal without precipitates for modeⅡ. Additionally, the shear force in (101)[10-1]was the largest, following was in (111)[-110] and (001)[100], It can be concluded that the shear process in (101)[10-1] was mostly affected by the precipitates. When containing a number of precipitates is contained, resistance of dislocation slip decrease with increasing distance of precipitates；For this reason, the instant shear stress was not enhanced obviously when the precipitates is encountered. However, with a decreasing spacing between precipitates, a higher driving force was needed to cross obstacles. Hence, as more dense precipitates existed in materials, the plastic shear stress was higher, The shear behavior in modeⅢ shows that the FCC crystal has {111} cleavage planes of brittle failure of the feature.

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